1. Field of the Invention
This invention relates to a liquid crystal display, and more particularly to a liquid crystal display and a driving method thereof that are capable of driving a liquid crystal display panel with no flicker using a data driver driven by a column inversion system.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) controls light transmittance for each liquid crystal cell in the LCD in accordance with a video signal to thereby display a picture. To this end, the LCD includes a liquid crystal display panel having liquid crystal cells arranged in a matrix type and a driving circuit for driving the liquid crystal display panel.
In the liquid crystal display panel, gate lines and data lines are arranged in such a manner to cross each other. A liquid crystal cell is positioned at each area where the gate lines cross the data lines. Each liquid crystal cell is provided with a pixel electrode and a common electrode for applying an electric field. Each pixel electrode is connected, via a thin film transistor as a switching device, to any one of data lines. The gate electrode of the thin film transistor is connected to any one of the gate lines, allowing a pixel voltage signal to be applied to the pixel electrodes for each one line.
The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, and a common voltage generator for driving the common electrode. The gate driver sequentially applies a scanning signal, that is, a gate signal, to the gate lines to thereby sequentially drive the liquid crystal cells on the liquid crystal display panel one line by one line. The data driver applies a video signal to each of the data lines whenever the gate signal is applied to any one of the gate lines. The common voltage generator applies a common voltage signal to the common electrode. Accordingly, the LCD changes an alignment of the liquid crystal molecules between the pixel electrode and the common electrode in accordance with a voltage applied to each liquid crystal cell to control a light transmittance, thereby displaying a picture.
For instance, as shown in FIG. 1, a related art liquid crystal display includes a liquid crystal display panel 2 having liquid crystal cells arranged in a matrix type, a gate driver 4 for driving gate lines GL1 to GLn of the liquid crystal display panel 2, and a data driver 6 for driving data lines DL1 to DLm of the liquid crystal display panel 2.
In FIG. 1, the liquid crystal display panel 2 includes liquid crystal cells arranged in a matrix type, and thin film transistors (TFTs), each of which are provided at a crossing between the n gate lines GL1 to GLn and the m data lines DL1 to DLm. The TFT applies a video signal from the data line DL1 to DLm to the liquid crystal cell in response to a gate signal from the gate lines GL1 to GLn. The liquid crystal cell can be expressed equivalently as a liquid crystal capacitor Clc including a common electrode opposed to a pixel electrode connected to the TFT with a liquid crystal therebetween. Further, the liquid crystal cell is provided with a storage capacitor (not shown) for maintaining a video signal voltage charged in the liquid crystal capacitor Clc until the next data voltage will be charged.
The storage capacitor is provided between a preceding gate electrode and pixel electrode. The gate driver 4 sequentially applies a gate signal to the gate lines GL1 to GLn to drive the TFT connected to the corresponding gate line. The data driver 6 converts video data into analog video signals to apply video signals for one horizontal line to the data lines DL1 to DLm during one horizontal period when a gate signal is applied to the gate line GL. In this case, the data driver 6 converts the video data into video signals with the aid of gamma voltages from a gamma voltage generator (not shown) to supply them.
Such a liquid crystal display device is provided with a color filter 8 as illustrated in FIG. 2. The color filter 8 includes a plurality of red (R), green (G) and blue (B) filters that are alternately arranged within each row to provide a color in each respective column resulting in a stripe shape. The red (R) color filter is provided on the liquid crystal cells and supplied with a red video data to convert light supplied from the liquid crystal cells into a red color. The green (G) color filter is provided on the liquid crystal cells and supplied with a green video signal to convert light from the liquid crystal cells into a green color. The blue (B) color filter is provided on the liquid crystal cells and supplied with a blue video signal to convert light from the liquid crystal cells into a blue color.
In order to drive the liquid crystal cells on the liquid crystal display panel, such a liquid crystal display uses an inversion driving method such as a frame inversion system, a line (or column) inversion system, or a dot inversion system.
In the frame inversion system, polarities of the video signals applied to the liquid crystal cells on the liquid crystal display panel are inverted whenever a frame is changed.
In the line inversion system, polarities of the video signals applied to the liquid crystal display panel are inverted every gate line of the liquid crystal display and every frame, as illustrated in FIG. 3A and FIG. 3B, respectively. Such a line inversion driving system has a problem in that crosstalk between horizontal pixels exists, causing flicker such as a stripe pattern between horizontal lines.
In the column inversion system, polarities of the video signals applied to the liquid crystal display panel are inverted in accordance with a data line of the liquid crystal display panel and in accordance with a frame, as illustrated in FIG. 4A and FIG. 4B, respectively. Such a column inversion driving system has a problem in that crosstalk between vertical pixels exists, causing flicker such as a stripe pattern between vertical lines.
In the dot inversion system, video signals having polarities opposite to the polarities of the video signals of all adjacent liquid crystal cells in the horizontal and vertical directions are applied to the liquid crystal cells, and the polarities of the video signals are inverted every frame, as illustrated in FIG. 5A and FIG. 5B. In other words, in the dot inversion system, when video signals at the odd-numbered frames are displayed, video signals are applied to the liquid crystal cells such that a positive (+) polarity and a negative (−) polarity are alternated from the left upper liquid crystal cells to the right liquid crystal cells and to the lower liquid crystal cells as illustrated in FIG. 5A; whereas, when video signals at the even-numbered frames are displayed, video signals are applied to the liquid crystal cells such that a positive (+) polarity and a negative (−) polarity are alternated from the left upper liquid crystal cells to the right liquid crystal cells and to the lower liquid crystal cells as illustrated in FIG. 5B. Such a dot inversion driving system cancels flicker occurring between the adjacent pixels, thereby providing more excellent picture quality in comparison to other inversion systems.
However, the dot inversion driving system has a disadvantage in that, since the polarities of the video signals applied from the data driver to the data lines should be inverted in the horizontal and vertical directions, a variation in the amount of the pixel voltage, that is, a frequency of the video signal, is larger than other inversion systems, causing an increase in power consumption.